The present invention relates generally to the field of magnetic tape readers, and more particularly to diagnosing and recovering from hardware failures in tunneling magnetoresistive sensors.
Tunneling magnetoresistive (“TMR”) sensors are microelectronic devices that are characterized by a change in electrical resistance in the presence or absence of a magnetic field. Magnetic storage devices, such as magnetic tape drives and hard disk drives, rely upon TMR sensors to read data from magnetic media. Different regions of magnetic media correspond to bits of data, each of which can apply either of two different magnetic field states to the TMR sensor. The value of each bit, one or zero, can be determined electronically by measuring resistance across the TMR sensor such that one state may be characterized by a relatively high resistance and the other characterized by a relatively low resistance.
As with all microelectronic devices, TMR sensors experience hardware failures of various kinds. In particular, TMR sensors are often located at an air bearing surface, which exposes them to various kinds of external damage. Using software, for example controller firmware or driver software that operates a tape drive or magnetic disk drive, engineers can diagnose and mitigate various failures, thereby allowing devices to continue to function despite some operational defect at the microelectronic device level. Also with the aid of software, engineers can diagnose failures in devices that have been rendered inoperable or subjected to failure analysis.